APPLICANT'S ABSTRACT: The proposed study arises from the need to develop effective treatment for adolescent girls with the dual diagnosis of posttraumatic stress disorder (PTSD) and alcohol use disorder (AUD). Adolescent girls with current PTSD Are estimated to comprise 40% OF AUD treatment samples (more than three times the rate for adolescent boys). There appears to be a serious public health need to intervene as early as possible for adolescents with this dual diagnosis to prevent the chronic course of these disorders into adulthood. As yet, no effective treatment for this substantial population has been identified. We propose to adapt for adolescent girls an existing manualized cognitive behavioral group therapy that was specifically designed for the integrated treatment of PTSD and alcohol/drug disorders. The therapy has evidenced strong initial empirical findings in an outcome study of adult women with PTSD and alcohol/drug use disorder, and would be customized in the proposed study to address the developmental and thematic concerns if adolescent girls. This 24 session, structured therapy offers intensive rehearsal of cognitive, behavioral, and interpersonal coping skills, using techniques empirically validated in the educational literature to make the treatment accessible and engaging. It is cost-sensitive (i.e., a group format), has been revised on the basis of actual experience and empirical results, and targets topics believed central for females with this dual diagnosis (e.g., how to set boundaries in interpersonal relationships). Its primary goals are abstinence from alcohol and drugs and reduction in PTSD symptoms. We also proposed to conduct an exploratory controlled outcome study comparing the adapted CB treatment to a treatment-as-usual (TAU) control condition, with 16 outpatient adolescent girls per condition using a sequential cohorts design and a 3-month follow-up. The study would evaluate the impact of the adapted group treatment within and between conditions in: reducing alcohol/drug use, PTSD symptoms, and other psychiatric and functioning variables; and within the CB treatment, would explore patient's level of satisfaction/alliance with the therapy and knowledge acquisition and self-reported use of CBT coping skills presented in the treatment. In addition, the study could (a) estimate the effect size of the treatment condition compared to the control condition, with reduction in alcohol use as the primary outcome measure; and (b) provide initial psychometric validation in an adolescent sample of two instruments that are theoretically derived from this treatment: a therapist adherence scale and a patient "core components of treatment" scale, which attempts to measure hypothesized mechanisms of action of the therapy.